1. Field of the Invention
The present invention relates to a tape carrier package, and more particularly, to a tape carrier package for preventing connection parts from eroding.
2. Discussion of the Related Art
Recently, as contemporary society develops toward an information society, importance of a flat panel display device as an information display device is gradually increasing. Particularly, due to features and advantages such as high image quality, lightweight, thinness, and low power consumption, the LCD is most widely used as a portable display device to substitute a cathode ray tube (CRT).
There are various flat panel display devices such as a liquid crystal display device (LCD), a plasma display panel (PDP), an electro-luminescence (EL) device, and the like. Generally, the flat panel display device includes a plurality of driver chips mounted therein to drive the flat panel display device.
The driver chip, among components mounted in the flat panel display device, is a very important component for determining performance of the flat panel display device.
In order to mount the driver chip to the flat panel display device, a tape carrier package (hereinafter referred to as ‘TCP’) is chiefly used.
Here, the TCP means a package utilizing a tape automated bonding technology for bonding a bump of the driver chip to an inner lead of the TCP by thermo-compression and for sealing the same with resin, as a wireless bonding method among the mounting technologies used in a highly integrated semiconductor chip such as an LSI.
When the TCP is used among the mounting methods of a driver chip in the flat panel display device, since costs for the package are decreased and the supply and attachment of the packages can be automatically performed, the TCP method is widely utilized.
FIG. 1 is a plan view illustrating a conventional tap tape of the TCP. For reference, this plan view depicts a tap tape for a single TCP, but actually, such tap tapes of the TCP are formed repeatedly.
As shown in the drawing, the tap tape of a TCP has a structure in that wiring patterns are formed by patterning copper (Cu) foil on a polyimide base film. In the base film 10, a device hole 11 is formed to mount the driver chips (not shown) by the inner bonding. Along the lateral sides of the base film 10, sprocket holes 12 are formed at a regular interval.
Here, the driver chips are mounted on the tap tape by bonding the bumps of the driver chips to the inner leads of the device holes 11 by the thermo-compression and coating the sealing resin thereon.
The sprocket holes 12 guide the alignment and movement of the tap tapes of the TCPs such that the tap tapes can be continuously supplied from a reel to another reel during the manufacturing of the tap tapes of the TCP.
The wiring patterns include input patterns 13 extending from the center of the device hole 11 to a side of the tap tape and output patterns 14 extending from the center of the device hole 11 to the other side of the tap tape. Here, the input patterns 13 are connected to a connector of a printed circuit board and the output patterns 14 are aligned with and connected to input pads of a panel of the flat panel display device. The wiring patterns made of the copper foil are coated with Sn or Au.
The base film 10 has first slits 15 and second slits 16 for distributing stress generated when bending the TCP. The first slit 15 and the second slits 16 are formed in regions of the sprocket holes 12 positioned at the lower side of the device hole 11.
Although individual tap tape of the TCP has been described above, actually, the tap tape of the TCP is wound around a taping roller in the form of a reel and must be cut off by a cutting machine having a specific shape such that the TCP is connected to the panel of the flat panel display device and the printed circuit board (PCB).
The input patterns of the conventional tap tape of the TCP, as shown in FIG. 2, are formed in the region outside a cutting line 20 to be cut by the cutting machine and has pads to be connected to the connector of the printed circuit board and having the same width. Parts formed in a region outside the cutting line 200 are test pads 40.
When the tap tape of the TCP is cut off by the cutting machine and separated from each other individually, as shown in FIG. 3, the TCP 50 is connected to the panel 60 of the flat panel display device and to a connector 75 of a printed circuit board 70 by which the output patterns are aligned with input pads of the panel 60 of the flat panel display device by the film 80 and the input patterns of the TCP 50 are connected to the connector 75 of the printed circuit board 70 disposed lower than the panel 60.
In a case of the PDP, the input patterns of the TCP 50 are connected to the printed circuit board 70 chiefly by the connector 75. Here, the state that the input patterns of the TCP are internally connected to the connector of the printed circuit board is depicted in FIGS. 4A and 4B.
As shown in the drawing, the connector 100 of the printed circuit board has plastic bodies 110 arranged at regular intervals and copper (Cu) pins 120 arranged between the bodies 110 at regular intervals.
When pads 130 of the input patterns of the TCP are connected to the connector 100, the pads 130 of the input patterns of the TCP electrically contact the pins 120 of the connector 100 for the electrical connection thereof. At this time, the pads 130 of the input patterns of the TCP contact the pins 120 of the connector 100 and the bodies 110 of the connector 100.
In the PDP, a very high voltage as a driving power is required, and when the PDP is used for a long time at a place where relative humidity is high, Sn plating layers of the connections where the pads 130 of the input patterns contact the bodies 110 of the connector 100 are eroded.
In other words, although the bodies 110 are made of insulator, the bodies 110 of the connector 100 are in a grounded state when a high voltage is applied to the pads 130 of the input patterns contacting the bodies 110 and humidity is high. At this time, due to the potential difference between the bodies 110 and the pads 130 of the input patterns, the Sn plating layers of the connections where the pads 130 of the input patterns contact the bodies 110 of the connector 100 are eroded.
Moreover, when the Sn plating layers of the input patterns are eroded, Cu patterns formed in the lower sides of the Sn plating layers are exposed to humidity. When the Cu patterns are exposed to humidity, the Cu patterns are eroded and electrical shorting is generated.
When plating layers are formed on the input patterns with Au, the pads 130 of the input patterns are minimally eroded even when the pads 130 contact the bodies 110 of the connector. However, the Au plating is expensive.